Once you feel a scratchy operation or can hear squeaking then it is advisable to apply a small amount of the lighter fluid, or something similar,onto a cotton bud and through the air flow slots in the casing, gently wipe over the contacts on the board.

Be sure not to bend the cable at the exit of the handle. The wiring will break from metal fatigue after a while and cause intermittent operation. Wind the cable into a gentle coil and it will last.